The invention relates to a feeder magazine for feeding to continuously operating film-developing machines, with guide rolls in the feeder magazine for the film material running into the film-developing machine, mounted on parallel shafts arranged one above the other. The lower shaft, on which the lower guide rolls are mounted, is mounted on a slide which can be moved on vertical columns.
The slide, which carries the lowest set of rolls, is referred to as the elevator which acts as a buffer for inserting a new spool of film, whose material extends about the upper and lower rolls, so that, when inserting a new roll of film, there is no need to interrupt the operation and particularly the discharging of the roll of film already inserted. Rather, the elevator ensures that a sufficient volume of film material is available for feeding, so that the film material is able to run continuously further into the film-developing machine, while a new spool is being inserted.
It is a disadvantage of the known feeder magazines that, should a tear occur in the film material which is running into or through the film-developing machine, especially while or shortly before a new spool of film is inserted, at which time the elevator has already moved up from its lower position, the elevator, because of its weight, moves downward relatively rapidly to its lowest position. As a result, the length of film material in the buffer or magazine increases and a corresponding amount of film material is retracted from the film-developing machine.
This leads to a situation in which film material, already developed or partially developed, is pulled in the opposite direction through the baths of the film-developing machine and may even return into the feeder magazine. As a consequence, in any case this part of the film material is disadvantageously affected and, under certain circumstances, may even become seriously damaged or totally unusable.
It is an object of the invention to avoid these disadvantages and to create a feeder magazine for continuously operating film-developing machines which, in case of a tear in or break of the film material, is not able to retract any film material from the film-developing machine and which does not exert any force on the film material, inserted or running out of the magazine, which would favor the formation of a tear or break.
This object is accomplished, in accordance with the invention, in the case of a feeder magazine of the type mentioned at the beginning, by the fact that at least one sensor, acting on one of the upper guide rolls and at least one brake, controlled by this sensor, are provided for the upper guide rolls and/or for the slide carrying the lower guide rolls. In so doing, each of the upper guide rolls has a sensor assigned to it, which, for example, is constructed as a lever, on the free end of which there is a feeler roll, which moves into a groove of the guide roll, when there is no film material running over this guide roll.
At the same time, all sensors are, preferably, mounted on a common shaft, which is constructed as a control element for the brake or brakes. Accordingly, the sensors are linked by an electrically conducting connection with this shaft and in each case has a contact, which can make contact with an electrically conducting rod, in order to close a control circuit when the various sensors are in particular position; namely, when they rest on film material running over the guide roll concerned. If at least one of the sensors is not resting on film material, and consequently can move into a groove of the guide roll concerned, contact with the electrically conducting rod and therefore with the control circuit is interrupted or closed, which immediately leads to an activation of the brake or brakes.
The brakes may be, for example, electromagnetic brakes. Preferably, two brakes are provided, one of which brakes the slide carrying the lower guide rolls, while the other brakes the upper guide rolls. At the same time, the brake for the upper guide rolls may have at least one axle, which is parallel to the shaft carrying the upper guide rolls and on which brake shoes are arranged, which can be displaced eccentrically, so that effective braking is achieved in the shortest displacement paths.
A further characteristic, with which a retraction of film material, which has already run into the film-developing machine, can be avoided, consists of the fact that the outlet roll of the feeder magazine, seated on the upper shaft, is equipped with a freewheeling system acting in one direction of rotation, so that this roll can be turned only in the outlet direction of the film material and not in the opposite direction.
In order to ensure a particularly easy running of the film material through the guide rolls which guide the feeder magazine, and in order to produce as little tension as possible in the film material, all guide rolls have, according to a further characteristic of the invention, extremely large ball bearings, and counter weights are arranged on the lower guide rolls. By these means, the danger of tearing the film material is reduced further.
Preferably, the sensors act together with several, and advisably with all of the upper guide rolls so that tearing of the film material at any position within the feeder magazine can be detected as quickly as possible and a braking effect brought about before the elevator or slide for the lower guide rolls has been displaced downwards by a detectable distance. When the slide for the lower guide rolls is braked practically immediately as the film material in the feeder magazine tears, there is no danger that the film material can be retracted from the film-developing machine into the feeder magazine. If the individual sensors are constructed as a whip roll, a particularly compact and safe operation of the control is possible .